All I know is that for a discrete variable such as this the expected value is the product of the number of trials and the probability of happening on each trial. Since in this case the probability of (Heads being shown) happening on each flip of the coin is the same then the expected value is where is the number of trials and is the probability of a heads being shown .

All I know is that for a discrete variable such as this the expected value is the product of the number of trials and the probability of happening on each trial. Since in this case the probability of (Heads being shown) happening on each flip of the coin is the same then the expected value is where is the number of trials and is the probability of a heads being shown .

Which in fact explains nothing, in a question like this we should relate the definition of the expected value to the data. So we sould either use the defintion that:

or that the number of heads is the sum of three RV's each of which has expectation (which using the definition of expected value is: ) and as expectation is additive the expected value of the sum is three times the individual expected values.

The bald statement in your post has no pedagogical (teaching) value so needs amplification.